Abstract
The rheometer, which measures the associated torque at controlled deformation, or, alternately, the associated deformation at controllable known torque, is an essential tool in food rheological studies. The modern rheometer consists of three main components: a measuring geometry, a torque transducer, and an angular displacement device. The geometry is very important; it is used to generate a particular deformation of a food material. In rheological measurements, the geometry is usually interchangeable and can be selected according to the physical state of the testing material. Thus, the selection of a measuring geometry (i.e., cone-plate, parallel plate, concentric cylinder, or capillary geometry) is critical if reliable and accurate rheological data are required.
In this review, the basic concepts of rheological properties (viscosity and viscoelasticity) are summarized; working equations of several commonly used geometries are presented; nonideality of geometries (i.e., end effect, slippage, viscous heating, etc.) are discussed; working equations of standard geometries are given; and, finally, the design philosophy of newly developed features of several commercial rheometers are addressed.
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